The common nitrogen-fixer in paddy fields is

1. Rhizobium

2. Azospirillum

3. Oscillatoria

4. Frankia

Which of the following is a symbiotic nitrogen fixer?

1. Glomus

2. Azotobacter

3. Frankia

4. Azolla

About 98 percent of the mass of every living organism is composed of just six elements

including carbon, hydrogen, nitrogen, oxygen and:

1. phosphorus and sulphur

2. sulphur and magnesium

3. magnesium and sodium

4. calcium and phosphorus

Which one of the following elements is not an essential micronutrient for plant growth?

1. Mn

2. Zn

3. Cu

4. Ca

A plant requires magnesium for

1. holding cells together

2. protein synthesis

3. chlorophyll synthesis

4. cell wall development

Farmers in a particular region were concerned that pre-mature yellowing of leaves of a pulse crop might cause a decrease in the yield. Which treatment could be most beneficial to obtain maximum seed yield?

1. Frequent irrigation of the crop

2. Treatment of the plants with cytokinins along with a small dose of nitrogenous fertilizer

3. Removal of all yellow leaves and spraying the remaining green leaves with 2, 4, 5 trichloro phenoxy acetic acid

4. Application of iron and magnesium to promote the synthesis of chlorophyll

Sulphur is an important nutrient for optimum growth and productivity in:

1. pulse crops

2. cereals

3. fibre crops

4. oilseed crops

The function of leghaemoglobin is

1. to provide oxygen to leg muscles of nitrogen-fixing

2. to protect oxygen-sensitive enzymes of nitrogen fixing bacteria in the root nodules of

legumes

3. to walk to the sites where oxygen is required

4. to function when haemoglobin is not available.

Hydroponics is

1. cultivation of plants in water

2. growth of plants towards water

3. growth of plants away from water

4. soilless cultivation of plants

The function of leghaemoglobin during biological nitrogen fixation in root nodules of legumes is to
1. convert atmospheric N₂ to NH₃
2. convert ammonia to nitrite
3. transport oxygen for activity of nitrogenase
4. protect nitrogenase from oxygen.